84 LOWER PTERYGOTA 



to cutting and biting the hairs, feathers, epidermal scales, 

 or excretions on the bodies of their hosts. The mandibles 

 are situated in most forms underneath the head and near 

 the centre, the clypeus projecting and forming the most 

 anterior portion of the head. The labrum is present and 

 the maxillary palpi are prominent in a part of the group. 

 The eyes when \'isible are located back of the antennae. 

 The antennae are five-jointed except in Trichodedes, where 

 they are three-jointed. The thorax is generally narrow and 



Fig. 45. — The cuninion hen louse (Menopon pallidum). Greatly 

 enlarged. (Banks, Div. Ent., U. S. Dept. Ag.) 



frequently but two di\'isions are apparent. The legs are 

 adapted to clasping (Philopterida') or to running (Liothe- 

 idse), the tarsi in the first case being short and in the latter 

 case being long, well adapted to running, and provided 

 with two claws. The members of the first division occur 

 on both mammals and birds, those of the second, except 

 Gyropus, are limited to birds. Wings are entirely wanting, 

 and the abdomen contains nine or ten segments and is 

 usually oval in shape. 

 The eggs are glued to the hairs or feathers of the host 



